Dominant Glint Based Prey Localization in Horseshoe Bats: A Possible Strategy for Noise Rejection

Rhinolophidae or Horseshoe bats emit long and narrowband calls. Fluttering insect prey generates echoes in which amplitude and frequency shifts are present, i.e. glints. These glints are reliable cues about the presence of prey and also encode certain properties of the prey. In this paper, we propose that these glints, i.e. the dominant glints, are also reliable signals upon which to base prey localization. In contrast to the spectral cues used by many other bats, the localization cues in Rhinolophidae are most likely provided by self-induced amplitude modulations generated by pinnae movement. Amplitude variations in the echo not introduced by the moving pinnae can be considered as noise interfering with the localization process. The amplitude of the dominant glints is very stable. Therefore, these parts of the echoes contain very little noise. However, using only the dominant glints potentially comes at a cost. Depending on the flutter rate of the insect, a limited number of dominant glints will be present in each echo giving the bat a limited number of sample points on which to base localization. We evaluate the feasibility of a strategy under which Rhinolophidae use only dominant glints. We use a computational model of the echolocation task faced by Rhinolophidae. Our model includes the spatial filtering of the echoes by the morphology of the sonar apparatus of Rhinolophus rouxii as well as the amplitude modulations introduced by pinnae movements. Using this model, we evaluate whether the dominant glints provide Rhinolophidae with enough information to perform localization. Our simulations show that Rhinolophidae can use dominant glints in the echoes as carriers for self-induced amplitude modulations serving as localization cues. In particular, it is shown that the reduction in noise achieved by using only the dominant glints outweighs the information loss that occurs by sampling the echo

Participación Política, Medios de Comunicación y Redes Sociales en los Adolescentes Catalanes

El grado de implicación política de los adolescentes es una cuestión abierta que atraviesa el debate académico generación tras generación. Actualmente, esta cuestión se ve salpicada por la irrupción de las redes sociales y los nuevos medios. El presente artículo estudia la vinculación entre el uso de medios, redes sociales y el interés por la política de una amplia muestra de estudiantes catalanes del último curso de Educación Secundaria Obligatoria. La investigación concluye que las dinámicas de participación política y las plataformas de debate de los adolescentes no difieren en exceso de las generaciones mayores y que, por tanto, las redes sociales no parecen haber afectado al grado de implicación política de los adolescentes

Vision-independent adjustment of unit tuning to sound localization cues in response to monaural occlusion in developing owl optic tectum

Neurons in the developing optic tectum adjust their tuning to auditory localization cues in response to chronic monaural occlusion so that auditory spatial fields align with visual receptive fields (VRFs). We tested whether this adaptive adjustment of auditory tuning requires visual instruction. Both eyelids were sutured closed at the same time that one ear was occluded in two barn owls that were 1 month old. After 70 and 100 d, respectively, the tuning of units to interaural level difference (ILD) and to interaural time difference (ITD) was measured. These data were compared with equivalent data from 15 normal owls. Unit tuning to ITD was shifted from normal in both of the monaurally occluded owls. In one owl, ILD tuning was also clearly shifted. In the other owl, the map of ILD was flipped upside down and adaptive adjustments in ILD tuning could not be assessed. Instead, adjustments in ILD tuning were observed following removal of the earplug with the eyelids kept closed. Unit tuning was monitored at several sites in the tectum for 1 month after earplug removal using chronically implanted electrodes. Then, ILD tuning was resampled across the entire tectum. Both measures indicated shifts in ILD tuning in response to removal of the earplug in the second blind owl. In both animals, the magnitude of the shifts in ILD tuning and ITD tuning was smaller than has been observed previously in monaurally occluded but sighted owls. The results demonstrate that the brain can make adaptive adjustments in ILD and ITD tuning in response to early monaural occlusion even without the guiding influence of vision.</jats:p

Hydrodynamic stimuli and the fish lateral line.

Bleckmann H, Engelmann J, Hanke W, Mogdans J. Hydrodynamic stimuli and the fish lateral line. Nature. 2002;408(6808):51-52

Design and fabrication process for artificial lateral line flow sensors

In fish the lateral line is a sensory organ used to perceive water movement in the surrounding environment to localize prey or predators, to avoid obstacles, for schooling and more. The lateral line consists of many mechanoreceptors called neuromast which consist of groups of hair cells covered by a jelly-like cupula. There are two types of neuromasts: superficial neuromasts which are situated on the skin, and canal neuromasts which are located canals that are connected to the water outside of the fish through a series of pores. We review design aspects for MEMS fabrication of capacitive hair based flow sensor arrays opera¬ting in aquatic environments, biomimicking neuromasts. Exploiting information gained from nature building a system that allows the study of hydrodynamic mechanical interactions in complex noisy environments may help to uncover more about nature and how to make reliable artificial systems

Ermittlung von Verfahrens- und Prozessparametern beim Innenhochdruckumformen von Hohlprofilen mit Nebenformelementen aus ebenen Zuschnitten Abschlussbericht

SIGLEAvailable from TIB Hannover: RO 146(87) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekArbeitsgemeinschaft Industrieller Forschungsvereinigungen 'Otto von Guericke' e.V. (AIF), Koeln (Germany); Bundesministerium fuer Wirtschaft, Bonn (Germany)DEGerman